In the past, soil cements have been used to stabilize road bases. However, prior known soil cements are susceptible to freeze-thaw cycles. Soil cements cannot be made impermeable to moisture penetration. Some soils such as clays and silts absorb large quantities of water. In addition, they often are poorly graded, allowing for significantly increased void space between the aggregate particles, which enhances permeability. When these soils are used to make soil cements, they become quite susceptible to freeze-thaw cycles, since no mechanism exists within the material to dissipate the internal pressure created by freezing water.
The process used in the creation and placement of soil cements is quite difficult and time consuming. To achieve the proper soil cement, the soil used must be as close to laboratory optimum moisture content as possible. Then, the typical soil cement must be compacted during placement to achieve the required bearing capabilities.
Several patents disclose soil stabilizing compounds and methods. For example, U.S. Pat. No. 4,871,283 to Wright discloses a soil cement for in-situ treatment and stabilization of subsurface soils by multiple point injection of a mixture of lime and fly ash in a slurry, which may incorporate additional cement and bentonite. This product and method strengthens the soil layers and controls the movement of subsurface water. Some of the specific uses of this compound are building roadbeds and stabilizing slopes. An apparent advantage of this technology is that the native soil layers were not first removed and then replaced. However, the Wright patent offers no solution to the freeze-thaw problem that inheres in soil cements.
U.S. Pat. No. 5,110,839 to Chao teaches a stabilized foam with fine pore sizes. This foam is used in light weight, cellular, cementitious products, especially building materials and structures where soundproofing, fire resistance, and decreased water permeability are desired. To the extent this technology might be used for road beds or soil stabilization, it is apparent that improving water resistance cannot be a long term solution. A similar scope is found U.S. Pat. No. 5,109,030 to the same inventor.
U.S. Pat. No. 4,077,809 to Plunguian et al discloses another stabilized foam for use in cellular concrete product designed for fire proofing, thermal insulation, and soundproofing. Air cells in various cementitious mixtures are stabilized by addition of an admixture of a water soluble organic film former, an emulsion of a synthetic resin, a mixture of anionic and non-ionic surfactants, and air to produce a stabilized foam. Foams of this type typically have a small, fine pore structure.
U.S. Pat. No. 4,965,097 to Bach discloses an earth confinement material that employs plastic, texturized strips to form air cells that hold fill material, such as of cement and aggregate.
Various surfactants have been used in soil stabilizing compounds. U.S. Pat. No. 4,545,820 to Mallow discloses a soil stabilizing compound that includes Portland cement, a hydrated alkali metal silicate powder and various other components necessitated by the presence of free water in the soil. The object is to stabilize indigenous soils for use in trench back fill and in road surfaces and subsurfaces. The compound has improved water resistance, which, as noted, is not a satisfactory solution to freeze-thaw problems. Further, this compound requires mechanical compaction after placement, which is undesirable.
U.S. Pat. No. 4,941,924 to Merritt teaches a chemical composition for stabilizing cohesive soils in roadbeds. The composition includes a large percentage of sulfuric acid and citrus stripper oil, and after application it must be compacted. The use of such chemicals on a roadway, coupled with mechanical compaction, is undesirable.
U.S. Pat. No. 3,887,506 to Hewitt discloses another formulation for stabilizing soils, such as road beds, by improving pavement sub-grades. The chemical applied is a combination of water diluted vinyl acetate polymer, a water repellant, and plasticizers, which are sprayed on native soils, mixed into the soil using typical road working equipment and mechanically compacted. The resultant sub-grade surface has increased compressive strength and decreased permeability. While this formulation might stabilize soils, it does not appear to stabilize the soil cement itself against typical freeze-thaw damage.
In light of the absence of a soil cement that, itself, is stable against freeze-thaw damage, it would be desirable to create a soil cement that incorporates an inherent release mechanism for internal hydraulic pressures, such as those pressures caused by freeze-thaw cycles, poorly graded materials, and water absorbing materials like clays.
Further, it would be desirable to create a soil cement that eliminates the mechanical compaction step associated with typical road base sub-grade enhancement, soil stabilization, geo-technical fills and trench back filling.
Since a road base may involve a large volume of material, it would be desirable to reduce cement content while increasing weather resistance and durability, as compared to standard lightweight concrete products.
Similarly, it would be desirable to use indigenous soils, certain granular waste products such as mill tailings, and commercially available aggregates as the aggregate portion of a mixture.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the product and method of application of this invention may comprise the following.